Air conditioning



March 14, 1950 w. MCGRATH AIR CONDITIONING Filed Dec. l, 1945 i IlIIIIAF? I I l INVENTOR. AMLZM., 4. 'NQ-f1 f BY 44M.; 2,

enema M. 14, 195o AIR CONDITIONING William L. McGrath, Syracuse, N. Y.,assignor to Carrier Corporation, Syracuse, N. Y., a corporation ofDelaware Application December 1, 1945, serial No. 632,153

This invention relates to air conditioning and to a method of.operatingan air conditioning system. y

An air conditioning system in extensive use contemplates the division ofa building into zones in accordance with the various heat loads presentin the rooms of the building. In such system air from the exterior ofthe building is treated at a central conditioning point remote from theareas to be conditioned to compensate for ventilation and dehumidicationrequirements of the various zones. It is then distributed at relativelyhigh static pressure and at relatively high velocity to a plurality ofunits disposed in and serving a plurality of areas to be conditioned inthe various zones. The high pressure air supplied to each unit isdischarged therein at high velocity inducing a relatively greatcirculation of air withdrawn from the areas served by the unit. Theprimary or high pressure air, and the secondary or induced air are thensupplied to the conditioned area. Tempering means such as coils or thelike are disposed in the various local units to effect heating orcooling of air circulated through the unit as required.

In the operation of the system cold water is furnished to the temperingmeans under summer conditions and Warm water is furnished to thetempering means under winter conditions. Depending upon the heat load ineach zone, cold or warm water may be supplied in winter or in summer.Under intermediate operating condi- 9 Claims. (Cl. 257-3) tions. somezones of the building are supplied withwarm Water while other zones ofthe building may be supplied with cold water.J

. In an air conditioning system of this character cold water is passedthrough a coil or washer in the air conditioning equipment to dehumidlfyair before it is supplied to the various local units in areas to beconditioned. Such cold water serves to reduce the dew point of the airto a desired degree. The refrigeration equipment required to supply coldwater for dehumidifying purposes is also required to supply cold waterto the various local units in order to eiect individual conditioning ofeach area in accordance with the variable heat factors present in sucharea.v It will be appreciated refrigerating equipment of great capacityls required for such equipment. must possess sullicient capacity todehumidify the air and to effect local cooling under maximum loadconditions. Consequently the cost of refrigerating equipment is a largefactor in the initial cost of the air conditioning system and theoperating expenses of such system are great since the system does notpossess sufficient flexibility to attain a reduction in operating costscommensurate with a reduction in the load imposed upon the system.

The chief object of the present invention is to provide a simplifiedcirculating system for conditioning medium used in an air conditioningsystem. v

An object of the invention is to provide a simplified circulating systemembodying control means which reduce the operating expenses of thesystem.

A further object is to provide a simplified air conditioning systemeconomical in initial and operating costs.

A still further object is to provide an air conditioning system in whichthe operating costs are reduced to a minimum.

A still further object is to provide a simpliiied method of operation ofan air conditioning system.

This invention relates to an air conditioning system including asimplified circulating system for conditioning medium. The circulatingsystem may comprise a source of supply of conditioning medium, means todirect conditioning medium from the supply through a heat exchangemember of air conditioning apparatus, a line connecting the heatexchange member to a common supply header, said header being adapted tosupply conditioning medium tol a plurality of zones of the airconditioning system, a supply main for each zone connected to theheader, lines connecting the supply mains to heat exchangers ofconditioning unts disposed in the areas to be conditioned, linesconnecting the unit heat exchangers to a common return header, a returnline connecting the return header and a second heat exchange member ofthe air conditioning apparatus, a line connecting the second heatexchange member to the source of supply, and means for passingconditioning medium through the system.

This invention further relates to a method of operation of an airconditioning system in which the steps comprise passing conditioningmedium from a source of supply to a heat exchange member in heatexchange relation with air to be conditioned, then forwarding theconditioning medium to a common supply header, passing conditioningmedium from the common header to a plurality of heat exchangers of unitsdisposed in zones to be conditioned, collecting conditioning medium fromthe unit heat exchangers in the zones in a common return header. passing3 conditioning medium from the return header to a second heat exchangerdisposed in heat exchange relation with the air to be conditioned andreturning the conditioning medium to the sourc of supply.

The attached drawing illustratesY diagrammatically a preferredembodiment of my invention.

Referring to the drawing, there is illustrated generally at 2 suitableair conditioning equipment for use in my invention. Such equipment mayinclude a preheater 3, a fan 4 adapted to draw air from the exterior ofthe building into the conditioning equipment, sprays 5, a precoolingcoil 6, and a dehumidifying coil 1. Fan 4 passes air to be conditionedthrough sprays 5, coil 6 and coil 1; if desired reheaters 8 may beprovided in the ducts (indicated by dotted lines) for supplying theconditioned air to conditioning units 9 disposed in areas I0 tobeconditioned. The various areas I to be conditioned may be arranged inzones in accordance with the variable heat factors present in each areato be conditioned.

At there is designated generally suitable refrigerating equipmentadapted to cool conditioning medium, for example, water, and supply ittothe coils 6 and 1 of air conditioning equipment 2 and heat exchangecoils of units 9 in areas I 0 to be conditioned. Such equipment maycomprise a centrifugal compressor I2, actuated by a suitable motor orturbine I3, connected to a Water cooler I4. A line I5 connects cooler I4with the-dehumidifying coil 1 of air conditioning equipment 2.Preferably, suitable means are provided to actuate compressor I2. Suchmeans may comprise a control I 6 adapted to govern the operation ofturbine or motor I3 and which in turn is actuated by means of athermostat I1 controlled by a bulb I8 placed in thermal contact withline I5.

Cold Water from coil 'i passes through line I9 to a supply header 2Ucommon to all the zones. Lines 2| connect header 20 with supply mains orrisers 22 serving the zones to be conditioned. Valves 23 are disposed inlines 2| for a purpose hereinafter explained. Conditioning medium passesfrom supply mains 22 through lines 24 to heat exchange members 25 in theform lof coils disposed in the units 9 in areas I0 to b conditioned.Cold Water from heat exchangers 25 passes through lines 26, lines 21,lines 28 to a common return header 29. Valves 30 are disposed in lines28 as hereinafter described.

Cold water from common return header 29 passes through return line 3| tothe precooling coil 6 of air conditioning equipment 2. A pump 32 isdisposed in line 3| as shown and a valve 33 is also disposed in line 3|between pump 32 and coil 6 for a purpose hereinafter described.' -Fromprecooling coil 6, cold water passes through line 34 connecting coil 6to the source of supply orcooler I4.

Under some conditions, for example when the various areas to beconditioned require only a small supply of cold water, the total ilow ofwater through precooling coil 6 and dehumidifying coil 1 may be reduced.Under such conditions, the' air being conditioned may not be conditionedadequately in accordance with the conditions encountered in the variousareas. To obviate this disadvantage, I provide a bypass 35 connectingline I9 and return line 3|. A valve 36 is disposed in bypass 35. Valve36 is actuated by a pressure differential control 31 which is actuatedby the difference in pressure of conditioning medium in lines 34 and I5.Control 31 measures the difference in pressure on the circuit and as thepressure drops, indicating a reduction in water ilow, valve 36 is openedand governed by control 31 to supply a substantially constant flow ofcold water through coil 6 and coil 1.

Suitable air vents 38 may be disposed in the stub ends of supply mains22 to permit air entrapped in the system to escape therefrom. Air vent39 may be disposed in the return header for the same purpose. Anexpansion tank 40 is pro- Xilded, header 29 being attached thereto by aline It will be appreciated that under winter conditions it may bedesired to supply warm water to all of the zones. Under intermediateoperating conditions lt may be desirable to supply warm water to some ofthe zones. I provide a heater 42 containing a steam coil 43 adapted toheat water for supply to the various zones. The amount of steam passingthrough coil 43 may be governed by a suitable thermostat 44 controlledby a bulb 45 disposed in thermal contact with a line 46 connectingheater 42 with a supply header 41. Thermostat 44 is adapted to actuate avalve 48 disposed in steam line 49 to increase or to decrease the amountof steam passing through coil 43.

Warm water passes from heater 42 through line 46 to supply header 41common to supply mains 22. Supply header 41 is connected to supply mains22 by means of lines 58, in which are disposed valves 5|. The Warm Waterthen passes through supply mains 22, lines 24, heat exchange members 25,lines 26, to lines 21. Lines 52 connect return header 53 with lines 21.Valves 54 are disposed in lines 52. Return header 53 is attached toexpansion tank 48 by means of line 4I and line 55. A return line 56connects return header 53 with a pump 51. A line 53 connects pump 51with heater 42. Valve 33 is disposed in line 58 as hereinafterdescribed.

When it is desired to supply hot water to the various zones, heater 42supplies the hot Water r through line 46 to supply header il common tothe zones. Hot water passes from header 41 through lines to risers 22disposed in the zones to be conditioned. Water then passes through lines24, heat exchangers 25, lines 26, lines 21, lines 52 to return header53. The Water is passed from return header 53 through line 56, pump 51,line 58 to heater 42.

It will be understood that when it is desired to supply hot water to azone, valves 5I and 54 will be opened and .valves 23 and 30 will beclosed. It is assumed that hot water is being supplied to all zones asis customary under winter operating conditions. When the system isoperated during intermediate conditions, for example, in the spring orin the fall, hot water may be supplied to some of the zones While coldwater is being supplied to the remaining zones.

Under conditions of maximum load requiring maximum cooling eiTect in theareas to be conditioned, it may be desired to use both lines 3| and 56as cold water return lines, and in some cases to use pump 51' to imposeadditional pressure upon cold lwater in the system serving in effect asan auxiliary to pump 32. For this purpose a line 59 is providedcontaining valve 60. Such line connects return lines 3| and 5E on oneside of pump 51. A second line 6I is also provided containing a valve 62which also connects return line 3| and line 58. When it is desired touse both lines 3| and 56 as return lines,

valve 60 is opened, valves l2 and 33' being closed, to permit water fromline 56 to iiow into line 3l. If it be desired to impose additionalpressure upon the cold water circulating in the system, valve 60 isclosed,` valve 33 remaining closed, and valve 62 opened permitting pump51' to impose additional pressure upon cold water in the system. It willbe Iunderstood, of course, valves 54 in the various zones are open topermit cold water to ow to header as.well as to header 29 and to returnthrough lines 56 and 3| to the precooling coil 6 of equipment 2 and thento the cooler Il. l l

While I have described the operation under conditions of maximum loadrequiring maximum to return the conditioning medium to the source ofsupply. and means for supplying the conditioned primary and secondaryair to the area to be conditioned.

` each zone connected to the header, unit heat cooling effect, it willbe understood it may be desired to use both 1ines'3l and 56 as hot Waterreturn lines under conditions requiring maximum cooling effect. Undersuch conditions, valves 62 and 33 are closed and valves 60 and 33'- areopened, to permit water from line 3| to 110WV into lines 56 and 58. Ifit be desired to impose additional pressure lupon the hot watercirculating in the system, valve 60 is closed, valve 33 remainingclosed, and valve 62 is opened permitting pump 32 to impose additionalpressure upon hot water in the system. The arrangement described ishighly advantageous since it permits both pumps to 'be used to imposepressure when operating under conditions requiring maximum coolingeffect or maximum heating effect and the system. The system is moresimple thansystems heretofore proposed. and consequently is moreeconomical in operation. In addition to the various economies in initialcost and operating costs mentioned above, it will be understood that aconsiderable reduction in initial cost is eiiected by the manner inwhich the circulating system is constructed; the system provided by myinvention eliminates approximately 50% or more of the piping heretoforedeemed necessary in an air conditioning system and thus effects a savingnot only in the cost of the piping but in the labor costs necessary toassemble the piping in the system.

While I have described a preferred embodiment of my invention, it willbe understood my invention is notlimited thereto since it may beotherwise embodied within the scope of the following claims.

I claim:

1. In an air conditioning system, the combination of means to conditionprimary air for supply to an area being conditioned, said meansincluding a rst heat exchange member, a second heat exchange member,means to pass air to be conditioned through said member, and a thirdheat exchange member disposed in heat exchange relation with secondaryair from the area to be conditioned, a source of supply for conditioningmedium, means for circulating conditioning medium from said source ofsupply through said rst heat exchange member,

then through said second heat exchange member exchangers disposed in theareas to be conditioned in heat exchange relation with secondary air tobe conditioned, lines connecting the supply main to said unit heatexchangers, a return header, lines connecting the unit heat exchangersto said return header, a return line, a second heat exchange member,means for passing primary air in heat exchange relation with the rst andsecond heat exchange members, said return line connecting the returnheader and said second heat exchange member, a line connecting thesecond heat exchange member with the source of supply means for passingconditioning medium through the system and means for supplying theconditioned primary and secondary air to the areas being conditioned.

3. A system according to claim 2 in which a bypass connects the supplyheader and the return line, a valve is disposed in said bypass, andmeans are provided to actuate said valve in response to a difference inpressure between conditioning medium in the rst means and conditioningmedium in the line connecting the second heat exchanger with the sourceof supply whereby upon a reduction in pressure, the valve is opened topermit water to ow from the supply to maintain a substantially constantilow of conditioning medium through the second heat exchange member andthe rst heat exchange member.

4. In an ai; conditioning system for a plurality of enclosed areasdisposed in zones, the combination of a source of supply of conditioningmedium, said source of supply including a refrigeration system forcooling the conditioning medium to predetermined temperature, a coil, aline connecting the source of supply with said coil, a supply headeradapted to supply conditioning medium' to a plurality of zones, a secondline connecting the coil and said supply header, a plurality of supplymains, lines connecting said supply header with said supply mains, eachsupply main being adapted to supply conditioning medium to a zone to beconditioned, unit coils disposed in the areas to be conditioned in heatexchange relation with secondary air to be conditioned, lines connectingthe supply mains to said unit coils, a, return header, lines connectingthe unit coils with said return header, a second coil, a return lineconnecting the return header with said second coil, means for passingprimary.

air in heat exchange relation with said rst and second coils, a lineconnecting said second coil with the source of supply, pump means forpassing conditioning medium through the circulating system' and meansfor supplying the conditioned primary and secondary air to the areasbeing conditioned.

5. A system according to claim 4 including a second source of supply forconditioning medium at a different temperature, a second supply header,a line connecting the second supply with a vsecond supply header, linesconnecting the second supply header with said supply mains, a

unit heat exchangers to the rst return header,

a second return line connecting the second return lheader with thesource of supply, and second pump means for passing the conditioningmedium from the second source of supply through the system.

6. A'system according to claim 5 in which valves are disposed in thelines connecting the supply mains and the first supply header, valvesare disposed in the lines connecting the supply t mains and the secondsupply header, valves are `line is disposed in the system connecting therst return line and the second return line, a valve is provided in saidline, a second line is disposed in the system connecting the ilrstreturn line and the second return line, and a second' valve is disposedin the second line, opening of `the ilrst valve permitting both returnlines to be employed for returning conditioning medium to the secondheat exchange member under peak load conditions while closing of theiirst valve and opening of the second valve permits the second pumpmeans to serve as an auxiliary for the rst pump means under peak loadconditions.

8. A system according to claim 4 in which a bypass is providedconnecting the return header and the return line, a valve is disposed insaid bypass and control means for said valve are provided, said control,means serving in response to a diierence in pressure of conditioningmedium in the rst line and the line connecting second i second returnheader, lines connecting the second return header with the linesconnecting the to permit conditioning medium from said supply header toflow into the return line.

9. In an air conditioning system, the combination of means to conditionair, said means including a precooling coil, a dehumidifying coil andmeans to pass air to be conditioned through the coils; a plurality ofareas to be conditioned, conditioning units in said areas adapted toreceive conditioned airi from the conditioning means, heat exchangers insaid units, said areas being disposed in zones, means for supplyingconditioned air to the unit, a source of supply for conditioning mediumincluding a refrigeration system for cooling the conditioning medium toa predetermined temperature, a line connecting the source of supply withthe dehumidifying coil, a common supply header, a second line connectingthe dehumidifying coil with said common supply header, a plurality ofsupply mains connected to said header, each main being adapted to supplyconditioning medium to said unit heat exchangers disposed in a zone, acommon return header, a line connecting the unit heat exchangers withthe return header, a return line connecting the precooling coil with thereturn header, a line connecting the precooling coil with the source ofsupply, pump means to pass conditioning medium throughout the sys` tem,a bypass connecting the supply header and the return line, a valve inlsaid bypass and control means to open and to close said valve tomaintain a substantially constant ow of conditioning medium through theprecooling coil and the dehumidifying coil WILLIAM L, McGRATH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,112,520 Crawford Mar. 29, 19382,304,243 Crawford Dec. 8, 1942

